//===-- secondary.h ---------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef SCUDO_SECONDARY_H_
#define SCUDO_SECONDARY_H_
#include "common.h"
#include "list.h"
#include "mutex.h"
#include "stats.h"
#include "string_utils.h"
namespace scudo {
// This allocator wraps the platform allocation primitives, and as such is on
// the slower side and should preferably be used for larger sized allocations.
// Blocks allocated will be preceded and followed by a guard page, and hold
// their own header that is not checksummed: the guard pages and the Combined
// header should be enough for our purpose.
namespace LargeBlock {
struct Header {
LargeBlock::Header *Prev;
LargeBlock::Header *Next;
uptr BlockEnd;
uptr MapBase;
uptr MapSize;
[[no_unique_address]] MapPlatformData Data;
};
constexpr uptr getHeaderSize() {
return roundUpTo(sizeof(Header), 1U << SCUDO_MIN_ALIGNMENT_LOG);
}
static Header *getHeader(uptr Ptr) {
return reinterpret_cast<Header *>(Ptr - getHeaderSize());
}
static Header *getHeader(const void *Ptr) {
return getHeader(reinterpret_cast<uptr>(Ptr));
}
} // namespace LargeBlock
class MapAllocatorNoCache {
public:
void initLinkerInitialized(UNUSED s32 ReleaseToOsInterval) {}
void init(UNUSED s32 ReleaseToOsInterval) {}
bool retrieve(UNUSED uptr Size, UNUSED LargeBlock::Header **H,
UNUSED bool *Zeroed) {
return false;
}
bool store(UNUSED LargeBlock::Header *H) { return false; }
bool canCache(UNUSED uptr Size) { return false; }
void disable() {}
void enable() {}
void releaseToOS() {}
bool setOption(Option O, UNUSED sptr Value) {
if (O == Option::ReleaseInterval || O == Option::MaxCacheEntriesCount ||
O == Option::MaxCacheEntrySize)
return false;
// Not supported by the Secondary Cache, but not an error either.
return true;
}
};
template <typename Config> class MapAllocatorCache {
public:
// Ensure the default maximum specified fits the array.
static_assert(Config::SecondaryCacheDefaultMaxEntriesCount <=
Config::SecondaryCacheEntriesArraySize,
"");
void initLinkerInitialized(s32 ReleaseToOsInterval) {
setOption(Option::MaxCacheEntriesCount,
static_cast<sptr>(Config::SecondaryCacheDefaultMaxEntriesCount));
setOption(Option::MaxCacheEntrySize,
static_cast<sptr>(Config::SecondaryCacheDefaultMaxEntrySize));
setOption(Option::ReleaseInterval, static_cast<sptr>(ReleaseToOsInterval));
}
void init(s32 ReleaseToOsInterval) {
memset(this, 0, sizeof(*this));
initLinkerInitialized(ReleaseToOsInterval);
}
bool store(LargeBlock::Header *H) {
bool EntryCached = false;
bool EmptyCache = false;
const u64 Time = getMonotonicTime();
const u32 MaxCount = atomic_load_relaxed(&MaxEntriesCount);
{
ScopedLock L(Mutex);
if (EntriesCount >= MaxCount) {
if (IsFullEvents++ == 4U)
EmptyCache = true;
} else {
for (u32 I = 0; I < MaxCount; I++) {
if (Entries[I].Block)
continue;
if (I != 0)
Entries[I] = Entries[0];
Entries[0].Block = reinterpret_cast<uptr>(H);
Entries[0].BlockEnd = H->BlockEnd;
Entries[0].MapBase = H->MapBase;
Entries[0].MapSize = H->MapSize;
Entries[0].Data = H->Data;
Entries[0].Time = Time;
EntriesCount++;
EntryCached = true;
break;
}
}
}
s32 Interval;
if (EmptyCache)
empty();
else if ((Interval = atomic_load_relaxed(&ReleaseToOsIntervalMs)) >= 0)
releaseOlderThan(Time - static_cast<u64>(Interval) * 1000000);
return EntryCached;
}
bool retrieve(uptr Size, LargeBlock::Header **H, bool *Zeroed) {
const uptr PageSize = getPageSizeCached();
const u32 MaxCount = atomic_load_relaxed(&MaxEntriesCount);
ScopedLock L(Mutex);
if (EntriesCount == 0)
return false;
for (u32 I = 0; I < MaxCount; I++) {
if (!Entries[I].Block)
continue;
const uptr BlockSize = Entries[I].BlockEnd - Entries[I].Block;
if (Size > BlockSize)
continue;
if (Size < BlockSize - PageSize * 4U)
continue;
*H = reinterpret_cast<LargeBlock::Header *>(Entries[I].Block);
*Zeroed = Entries[I].Time == 0;
Entries[I].Block = 0;
(*H)->BlockEnd = Entries[I].BlockEnd;
(*H)->MapBase = Entries[I].MapBase;
(*H)->MapSize = Entries[I].MapSize;
(*H)->Data = Entries[I].Data;
EntriesCount--;
return true;
}
return false;
}
bool canCache(uptr Size) {
return atomic_load_relaxed(&MaxEntriesCount) != 0U &&
Size <= atomic_load_relaxed(&MaxEntrySize);
}
bool setOption(Option O, sptr Value) {
if (O == Option::ReleaseInterval) {
const s32 Interval =
Max(Min(static_cast<s32>(Value),
Config::SecondaryCacheMaxReleaseToOsIntervalMs),
Config::SecondaryCacheMinReleaseToOsIntervalMs);
atomic_store_relaxed(&ReleaseToOsIntervalMs, Interval);
return true;
} else if (O == Option::MaxCacheEntriesCount) {
const u32 MaxCount = static_cast<u32>(Value);
if (MaxCount > Config::SecondaryCacheEntriesArraySize)
return false;
atomic_store_relaxed(&MaxEntriesCount, MaxCount);
return true;
} else if (O == Option::MaxCacheEntrySize) {
atomic_store_relaxed(&MaxEntrySize, static_cast<uptr>(Value));
return true;
}
// Not supported by the Secondary Cache, but not an error either.
return true;
}
void releaseToOS() { releaseOlderThan(UINT64_MAX); }
void disable() { Mutex.lock(); }
void enable() { Mutex.unlock(); }
private:
void empty() {
struct {
void *MapBase;
uptr MapSize;
MapPlatformData Data;
} MapInfo[Config::SecondaryCacheEntriesArraySize];
uptr N = 0;
{
ScopedLock L(Mutex);
for (uptr I = 0; I < Config::SecondaryCacheEntriesArraySize; I++) {
if (!Entries[I].Block)
continue;
MapInfo[N].MapBase = reinterpret_cast<void *>(Entries[I].MapBase);
MapInfo[N].MapSize = Entries[I].MapSize;
MapInfo[N].Data = Entries[I].Data;
Entries[I].Block = 0;
N++;
}
EntriesCount = 0;
IsFullEvents = 0;
}
for (uptr I = 0; I < N; I++)
unmap(MapInfo[I].MapBase, MapInfo[I].MapSize, UNMAP_ALL,
&MapInfo[I].Data);
}
void releaseOlderThan(u64 Time) {
ScopedLock L(Mutex);
if (!EntriesCount)
return;
for (uptr I = 0; I < Config::SecondaryCacheEntriesArraySize; I++) {
if (!Entries[I].Block || !Entries[I].Time || Entries[I].Time > Time)
continue;
releasePagesToOS(Entries[I].Block, 0,
Entries[I].BlockEnd - Entries[I].Block,
&Entries[I].Data);
Entries[I].Time = 0;
}
}
struct CachedBlock {
uptr Block;
uptr BlockEnd;
uptr MapBase;
uptr MapSize;
[[no_unique_address]] MapPlatformData Data;
u64 Time;
};
HybridMutex Mutex;
CachedBlock Entries[Config::SecondaryCacheEntriesArraySize];
u32 EntriesCount;
atomic_u32 MaxEntriesCount;
atomic_uptr MaxEntrySize;
uptr LargestSize;
u32 IsFullEvents;
atomic_s32 ReleaseToOsIntervalMs;
};
template <typename Config> class MapAllocator {
public:
void initLinkerInitialized(GlobalStats *S, s32 ReleaseToOsInterval = -1) {
Cache.initLinkerInitialized(ReleaseToOsInterval);
Stats.initLinkerInitialized();
if (LIKELY(S))
S->link(&Stats);
}
void init(GlobalStats *S, s32 ReleaseToOsInterval = -1) {
memset(this, 0, sizeof(*this));
initLinkerInitialized(S, ReleaseToOsInterval);
}
void *allocate(uptr Size, uptr AlignmentHint = 0, uptr *BlockEnd = nullptr,
FillContentsMode FillContents = NoFill);
void deallocate(void *Ptr);
static uptr getBlockEnd(void *Ptr) {
return LargeBlock::getHeader(Ptr)->BlockEnd;
}
static uptr getBlockSize(void *Ptr) {
return getBlockEnd(Ptr) - reinterpret_cast<uptr>(Ptr);
}
void getStats(ScopedString *Str) const;
void disable() {
Mutex.lock();
Cache.disable();
}
void enable() {
Cache.enable();
Mutex.unlock();
}
template <typename F> void iterateOverBlocks(F Callback) const {
for (const auto &H : InUseBlocks)
Callback(reinterpret_cast<uptr>(&H) + LargeBlock::getHeaderSize());
}
uptr canCache(uptr Size) { return Cache.canCache(Size); }
bool setOption(Option O, sptr Value) { return Cache.setOption(O, Value); }
void releaseToOS() { Cache.releaseToOS(); }
private:
typename Config::SecondaryCache Cache;
HybridMutex Mutex;
DoublyLinkedList<LargeBlock::Header> InUseBlocks;
uptr AllocatedBytes;
uptr FreedBytes;
uptr LargestSize;
u32 NumberOfAllocs;
u32 NumberOfFrees;
LocalStats Stats;
};
// As with the Primary, the size passed to this function includes any desired
// alignment, so that the frontend can align the user allocation. The hint
// parameter allows us to unmap spurious memory when dealing with larger
// (greater than a page) alignments on 32-bit platforms.
// Due to the sparsity of address space available on those platforms, requesting
// an allocation from the Secondary with a large alignment would end up wasting
// VA space (even though we are not committing the whole thing), hence the need
// to trim off some of the reserved space.
// For allocations requested with an alignment greater than or equal to a page,
// the committed memory will amount to something close to Size - AlignmentHint
// (pending rounding and headers).
template <typename Config>
void *MapAllocator<Config>::allocate(uptr Size, uptr AlignmentHint,
uptr *BlockEnd,
FillContentsMode FillContents) {
DCHECK_GE(Size, AlignmentHint);
const uptr PageSize = getPageSizeCached();
const uptr RoundedSize =
roundUpTo(Size + LargeBlock::getHeaderSize(), PageSize);
if (AlignmentHint < PageSize && Cache.canCache(RoundedSize)) {
LargeBlock::Header *H;
bool Zeroed;
if (Cache.retrieve(RoundedSize, &H, &Zeroed)) {
if (BlockEnd)
*BlockEnd = H->BlockEnd;
void *Ptr = reinterpret_cast<void *>(reinterpret_cast<uptr>(H) +
LargeBlock::getHeaderSize());
if (FillContents && !Zeroed)
memset(Ptr, FillContents == ZeroFill ? 0 : PatternFillByte,
H->BlockEnd - reinterpret_cast<uptr>(Ptr));
const uptr BlockSize = H->BlockEnd - reinterpret_cast<uptr>(H);
{
ScopedLock L(Mutex);
InUseBlocks.push_back(H);
AllocatedBytes += BlockSize;
NumberOfAllocs++;
Stats.add(StatAllocated, BlockSize);
Stats.add(StatMapped, H->MapSize);
}
return Ptr;
}
}
MapPlatformData Data = {};
const uptr MapSize = RoundedSize + 2 * PageSize;
uptr MapBase =
reinterpret_cast<uptr>(map(nullptr, MapSize, "scudo:secondary",
MAP_NOACCESS | MAP_ALLOWNOMEM, &Data));
if (UNLIKELY(!MapBase))
return nullptr;
uptr CommitBase = MapBase + PageSize;
uptr MapEnd = MapBase + MapSize;
// In the unlikely event of alignments larger than a page, adjust the amount
// of memory we want to commit, and trim the extra memory.
if (UNLIKELY(AlignmentHint >= PageSize)) {
// For alignments greater than or equal to a page, the user pointer (eg: the
// pointer that is returned by the C or C++ allocation APIs) ends up on a
// page boundary , and our headers will live in the preceding page.
CommitBase = roundUpTo(MapBase + PageSize + 1, AlignmentHint) - PageSize;
const uptr NewMapBase = CommitBase - PageSize;
DCHECK_GE(NewMapBase, MapBase);
// We only trim the extra memory on 32-bit platforms: 64-bit platforms
// are less constrained memory wise, and that saves us two syscalls.
if (SCUDO_WORDSIZE == 32U && NewMapBase != MapBase) {
unmap(reinterpret_cast<void *>(MapBase), NewMapBase - MapBase, 0, &Data);
MapBase = NewMapBase;
}
const uptr NewMapEnd = CommitBase + PageSize +
roundUpTo((Size - AlignmentHint), PageSize) +
PageSize;
DCHECK_LE(NewMapEnd, MapEnd);
if (SCUDO_WORDSIZE == 32U && NewMapEnd != MapEnd) {
unmap(reinterpret_cast<void *>(NewMapEnd), MapEnd - NewMapEnd, 0, &Data);
MapEnd = NewMapEnd;
}
}
const uptr CommitSize = MapEnd - PageSize - CommitBase;
const uptr Ptr = reinterpret_cast<uptr>(
map(reinterpret_cast<void *>(CommitBase), CommitSize, "scudo:secondary",
MAP_RESIZABLE, &Data));
LargeBlock::Header *H = reinterpret_cast<LargeBlock::Header *>(Ptr);
H->MapBase = MapBase;
H->MapSize = MapEnd - MapBase;
H->BlockEnd = CommitBase + CommitSize;
H->Data = Data;
if (BlockEnd)
*BlockEnd = CommitBase + CommitSize;
{
ScopedLock L(Mutex);
InUseBlocks.push_back(H);
AllocatedBytes += CommitSize;
if (LargestSize < CommitSize)
LargestSize = CommitSize;
NumberOfAllocs++;
Stats.add(StatAllocated, CommitSize);
Stats.add(StatMapped, H->MapSize);
}
return reinterpret_cast<void *>(Ptr + LargeBlock::getHeaderSize());
}
template <typename Config> void MapAllocator<Config>::deallocate(void *Ptr) {
LargeBlock::Header *H = LargeBlock::getHeader(Ptr);
const uptr Block = reinterpret_cast<uptr>(H);
const uptr CommitSize = H->BlockEnd - Block;
{
ScopedLock L(Mutex);
InUseBlocks.remove(H);
FreedBytes += CommitSize;
NumberOfFrees++;
Stats.sub(StatAllocated, CommitSize);
Stats.sub(StatMapped, H->MapSize);
}
if (Cache.canCache(CommitSize) && Cache.store(H))
return;
void *Addr = reinterpret_cast<void *>(H->MapBase);
const uptr Size = H->MapSize;
MapPlatformData Data = H->Data;
unmap(Addr, Size, UNMAP_ALL, &Data);
}
template <typename Config>
void MapAllocator<Config>::getStats(ScopedString *Str) const {
Str->append(
"Stats: MapAllocator: allocated %zu times (%zuK), freed %zu times "
"(%zuK), remains %zu (%zuK) max %zuM\n",
NumberOfAllocs, AllocatedBytes >> 10, NumberOfFrees, FreedBytes >> 10,
NumberOfAllocs - NumberOfFrees, (AllocatedBytes - FreedBytes) >> 10,
LargestSize >> 20);
}
} // namespace scudo
#endif // SCUDO_SECONDARY_H_
